Re: [PATCH v5 1/2] cpufreq: CPPC: Set CPPC Enable register in cpu_init

[Sumit Gupta]

On 05/11/26 15:21, Jiri Benc wrote:
> External email: Use caution opening links or attachments
>
>
> On Tue, 23 Jun 2026 13:36:51 +0530, Sumit Gupta wrote:
> > As per ACPI 6.x s8.4.6.1.4 (CPPC Enable register):
> >    "If supported by the platform, OSPM writes a one to this register
> >     to enable CPPC on this processor. If not implemented, OSPM assumes
> >     the platform always has CPPC enabled."
> >
> > Call cppc_set_enable() at the start of cppc_cpufreq_cpu_init() so
> > this is done for both OS-driven and autonomous CPPC control modes.
> > Errors are logged but non-fatal as the register is optional.
>
> Sumit, given this is a bug fix to the CPPC driver (e.g. NVIDIA GB10
> doesn't enable CPPC without writing the register, keeping the CPUs
> always at the lowest freq) and is largely unrelated to the autonomous
> mode feature, could you please resubmit this as a standalone patch?
>
> Thanks!
>
>   Jiri

Posted separately.

https://lore.kernel.org/lkml/20261105123244.3132560-1-sumitg@xxxxxxxxxx/

Thanks,
Sumit


> > Signed-off-by: Sumit Gupta <sumitg@xxxxxxxxxx>
> > ---
> >   drivers/cpufreq/cppc_cpufreq.c | 8 ++++++++
> >   1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
> > index f6cea0c54dd9..f7a47576717a 100644
> > --- a/drivers/cpufreq/cppc_cpufreq.c
> > +++ b/drivers/cpufreq/cppc_cpufreq.c
> > @@ -655,6 +655,14 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
> >        caps = &cpu_data->perf_caps;
> >        policy->driver_data = cpu_data;
> >
> > +     /*
> > +      * Enable CPPC for both OS-driven and autonomous modes.
> > +      * The Enable register is optional - some platforms may not support it
> > +      */
> > +     ret = cppc_set_enable(cpu, true);
> > +     if (ret && ret != -EOPNOTSUPP)
> > +             pr_warn("Failed to enable CPPC for CPU%d (%d)\n", cpu, ret);
> > +
> >        /*
> >         * Set min to lowest nonlinear perf to avoid any efficiency penalty (see
> >         * Section 8.4.7.1.1.5 of ACPI 6.1 spec)